We have

a. If we graph the function given we will obtain a line, also we have a function with degree one, this is a characteristic of a liner function.
the form

is a form of a linear function where m is the slope and b is the y-intercept.
b. as we can see our slope is -0.139 because the slope is negative the value of the function will decrease when x is bigger, so we have more unmarried women because the marriage decrease when x is bigger also the slope is the rate of change.